def getLevel1(score):
    if score >= 90:
        return "A"
    elif score > 80:
        return "B"
    elif score > 60:
        return "C"
    else:
        return "D"




if __name__ == '__main__':
    score = float(input("请输入成绩："))
    level_ = getLevel1(score)
    print(level_)
